The integration of hundreds of millions of circuit elements, such as transistors, on a single integrated circuit necessitates further dramatic scaling down or micro-miniaturization of the physical dimensions of circuit elements, including interconnection structures. Micro-miniaturization has engendered a dramatic increase in transistor engineering complexity, such as the inclusion of graded well-doping, epitaxial wafers, halo implants, tip implants, lightly doped drain structures, multiple implants for source/drain regions, silicidation of gates and source/drains, and multiple sidewall spacers.
The drive for high performance requires high speed operation of microelectronic components requiring high drive currents in addition to low leakage, i.e., low off-state current, to reduce power consumption. Typically, the structural and doping parameters tending to provide a desired increase in drive current adversely impact leakage current.
As device geometries continue to plunge into the deep submicron regime, it is necessary to reduce the polysilicon depletion. Conventional approaches comprise replacing the high resistivity polysilicon gate with a metal gate or replacing the gate dielectric with a high-k material, such as a tantalum oxide, e.g., Ta2O5, or tantalum oxynitride (TaON). Conventional tantalum oxide deposition techniques include metal oxide chemical vapor deposition (MOCVD) or atomic layer deposition (ALD) techniques. Such attempts are plagued with several disadvantages. For example, chemical vapor deposition (CVD) techniques generate a high carbon content within the deposited film. Carbon is believed to be a major source for leakage and thermal instability. Replacement of conventional CVD or ALD deposition tools is very costly.
Accordingly, there exists a need for methodology enabling the fabrication of semiconductor devices having replacement metal gates and high-k dielectric layers with reduced carbon and, hence, reduced leakage and reduced thermal instability. There exists a particular need for such methodology without resorting to expensive replacement tools.